Although senators working on the bill have stressed that the document still isn't finalized, some important details have leaked in the past week.

Here's what you need to know:

1. The Border Security "Trigger"
The bill creates a pathway to citizenship for undocumented immigrants who meet certain qualifications, but applicants would need to undergo a 10-year probationary period before being eligible for a green card.

The decade-long wait comes with another caveat: The federal government will need to meet certain border security benchmarks before any undocumented immigrants can receive a green card.

The benchmarks? An operational border security plan, a completed border fence, a mandatory employment verification system across the country and a system to track exits at airports and seaports, according to reports in several news outlets.

The border security plan would require surveillance of 100 percent of the U.S.-Mexico border and 90 percent effectiveness in border enforcement, The New York Times reported.

If those goals are met, immigrants who completed the 10-year waiting period would be eligible to apply for a green card.

2. The Cut-Off Date
Of the estimated 11 million undocumented immigrants in the U.S., hundreds of thousands may not be eligible for the path to citizenship being offered by the Senate, the AP reported on Friday.

The bill requires that applicants prove they were in the country before December 31, 2011, the AP reported. That means anyone who arrived after that date would be excluded.

There will be other requirements, too, like proving you have a clean criminal record and that you have enough job stability to stay off welfare. How the bill defines those things -- criminality and financial stability -- could decide the fate of thousands.

3. More Visas for Workers
The majority of immigrants who receive legal permanent residence in the U.S. get their visas because of family ties.

But the Senate bill will add a major new "merit-based" program, The New York Times reported on Thursday.

Here's what will happen, according to the Times:

Over a 10-year period, the government will seek to clear the backlog of 4.7 million immigrants waiting to come to the U.S.

After that, the bill will create a new, merit-based visa program that will offer legal permanent residence based on work skills.

At the same time, some family-based visas will be eliminated. Siblings of U.S. citizens would no longer be eligible for green cards, the documents that show legal permanent residence.

The exact balance of family visas to employment visas in the Senate proposal isn't clear, but the bill would focus on bringing in more workers of all skill levels.